Physics (10th Edition)

Published by Wiley
ISBN 10: 1118486897
ISBN 13: 978-1-11848-689-4

Chapter 10 - Simple Harmonic Motion and Elasticity - Problems - Page 277: 47

Answer

Both pendulums have the same period $T=1.64s$

Work Step by Step

In a physical pendulum, $$\frac{2\pi}{T}=\sqrt{\frac{mgL}{I}}$$ $$T=\frac{2\pi}{\sqrt{\frac{mgL}{I}}}=2\pi\sqrt{\frac{I}{mgL}}$$ We take the stick's length to be $R$. The stick's moment of inertia is $I=\frac{1}{3}mR^2$. The stick's center of gravity is at its center, so the length of the pendulum here $L=R/2$ $$T=2\pi\sqrt{\frac{mR^2}{3mg\frac{R}{2}}}=2\pi\sqrt{\frac{2R}{3g}}$$ As we can see from here, the equation of $T$ does not change according to the mass of the sticks. Therefore, the period of both pendulums is the same. The sticks are meter sticks, so $R=1m$. The pendulum's period is $$T=1.64s$$
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